A known failure mechanism for spark plugs in combustion engines is the failure of the ground or side electrode due to service in oxidizing conditions and at elevated temperatures. Currently, a sphere of precious metal alloy is resistance welded to the Ni-based super alloy ground electrode. This tip and weld is often the nucleation point for failure. Spark plug failure can result from poorer spark erosion resistance due to oxidation of the electrode, scale formation resulting in increased spark resistance, and oxidation of the electrode-tip interface leading to increased spark resistance or the tip falling off. Cost savings is also a driving force. By improving the weld interface and/or using a more erosion resistant tip material, one can increase the spark plug life. However, better tip materials have been shown to cause resistance welding difficulties.
Standard spark plugs are manufactured by welding a precious metal or precious metal alloy tip to a ground electrode of some base material (typically nickel-based alloy). The precious metal tip composition is such that it can be welded to the base side electrode material. However, this weld can fail due to several causes, some of which were previously mentioned. Also, some tip materials (such as iridium and iridium based alloys), which have been shown to perform better in spark plug applications than the current practice of platinum-based alloys, are extremely difficult to weld resistively.
Accordingly, it is desirable to provide a side electrode for spark plugs designed to have a side wire/electrode tip attachment that is less susceptible to failure and has an electrode tip formed from erosion resistant tip materials.